TMG Supplement: Benefits, Dosage, Safety, and Smart Use

TMG (trimethylglycine) is a popular supplement for homocysteine support and potential performance benefits—here’s what the evidence actually says and how to use it safely.

• What it is: TMG (also called betaine) is a natural compound from foods like beets that helps recycle homocysteine and supports cellular hydration.
• Why people take it: To help lower homocysteine (a heart‑health marker) and for possible, small performance boosts in some training contexts.
• Typical doses: About 2.5–3 g/day for performance research; 4–6 g/day in studies targeting homocysteine, based on a 2013 meta‑analysis of randomized trials.
• Safety watch‑outs: At 6 g/day, some trials reported rises in LDL and triglycerides—so monitor your lipids if you supplement, especially at higher intakes, as shown in a 2005 randomized trial and discussed in a PLOS Medicine commentary.
• First steps before TMG: Ensure folate and vitamin B12 status are dialed in when addressing homocysteine.

Educational only, not medical advice. Check with your clinician before starting any supplement.

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Key takeaways

• Methyl donor: TMG helps your body recycle homocysteine back into methionine—supporting healthy methylation.
• Osmolyte: It helps cells stay resilient and hydrated under stress (like heat or dehydration), especially in the liver, kidneys, gut, and fat tissue, according to a 2021 Nutrients review.
• Homocysteine: TMG reliably lowers homocysteine at 4–6 g/day, but trials haven’t shown clear improvements in blood‑vessel function or heart outcomes, based on a 2013 meta‑analysis and a 6‑week randomized FMD trial.
• Lipids: Higher doses (e.g., 6 g/day) have raised LDL and triglycerides in healthy adults, as shown in a 2005 clinical trial.
• Performance: A few studies have found small sprint or cycling time‑trial improvements at ~2.5–3 g/day (e.g., a 2012 JISSN trial and a 2024 Nutrients study), but a 2017 review rates the evidence as inconsistent.
• Medical use is different: For genetic homocystinuria, prescription betaine is used under physician supervision due to risks like hypermethioninemia, per the FDA Cystadane label.

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What is a TMG supplement (trimethylglycine)?

Think of TMG as part nutrient, part cellular bodyguard.

• Where your body uses it: The BHMT pathway—active mainly in the liver and kidneys—uses TMG to remethylate homocysteine back to methionine. This route complements (but doesn’t replace) the folate/B12‑dependent pathway. If you have a folate or B12 deficiency, correcting it is the first priority. While the TMG pathway can help, it cannot fix a vitamin deficiency on its own, as summarized in the 2021 Nutrients review.
• How you get it: Your body can make betaine from choline, and you can eat it directly in foods like beets, spinach, and whole grains. Typical diets provide hundreds of milligrams per day; supplements deliver gram‑level amounts for targeted effects, according to the 2021 Nutrients review.
• Why athletes care: As an osmolyte, TMG helps proteins keep their shape under stress and supports fluid balance—mechanisms that may explain small performance findings in some studies (see trials below and the 2021 Nutrients review).

Benefits: what the evidence says (and where it’s shaky)

1) Homocysteine support

• Consistent reduction: Randomized trials show 4–6 g/day lowers plasma homocysteine by roughly 1–2 μmol/L in generally healthy adults, according to a 2013 meta‑analysis.
• But outcomes are unclear: Lower homocysteine hasn’t translated into better blood‑vessel function in short trials; one 6‑week study found no improvement in flow‑mediated dilation (FMD) with either folic acid or TMG in older adults, in a randomized trial.
• Consideration: impact on lipids: At 6 g/day, LDL and triglycerides increased in healthy adults; smaller increases may appear at lower doses. Evidence comes from a 2005 clinical trial and a PLOS Medicine commentary.

Bottom line: If homocysteine is your primary target, most clinicians start with folate and B12 first. TMG can be an adjunct—just add lipid monitoring.

2) Athletic performance (mixed)

• Power: About 2.5 g/day for 1 week increased cycling sprint power by ~3–6% in one study, shown in a 2012 JISSN randomized trial.
• Endurance: 3 g/day for 2 weeks modestly improved a 60‑km cycling time trial in trained cyclists in a 2024 Nutrients study.
• Overall: A 2017 review characterizes the performance evidence as inconsistent with generally small effects.

3) Liver and metabolic health (emerging)

Early research hints TMG may support fatty‑liver improvements and antioxidant defenses, but much of this is preclinical or from small human studies—promising, not proven yet, according to a 2021 comprehensive review in Nutrients. If insulin resistance is part of your picture, our Insulin Resistance & Weight Loss Guide lays out a practical plan.

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Safety, side effects, and who should skip it

• Cholesterol and triglycerides: Expect possible rises with higher doses (notably at 6 g/day). Consider a baseline and 6–8‑week follow‑up lipid panel if using ≥3 g/day, based on a 2005 randomized trial.
• GI upset: Nausea, diarrhea, bloating, and stomach discomfort can occur—especially at larger doses (also seen with prescription betaine), per the FDA Cystadane label.
• Genetic homocystinuria (CBS deficiency): Prescription betaine is used medically but can cause very high methionine and rare cerebral edema—this requires physician supervision, per the FDA label.
• Pregnancy, nursing, children: Safety data are limited—avoid unless your clinician advises otherwise.
• Medication or vitamin status: If you’re targeting homocysteine, discuss folate/B12 status and medications that affect one‑carbon metabolism with your clinician.

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How much TMG should you take?

Your dose depends on your goal. Use these research‑based ranges as a starting framework and personalize with your clinician.

• Homocysteine support: Many trials used 4–6 g/day, split into 2 doses. Prioritize folate/B12 first; add TMG cautiously and monitor lipids, as reported in a 2013 meta‑analysis and a 2005 clinical trial.
• Performance: 2.5–3 g/day for 1–2 weeks has shown small improvements in some sprint and cycling studies, including a 2012 JISSN trial and a 2024 Nutrients time‑trial study.
• Stacking with B‑vitamins: A low‑dose B‑vitamin + betaine combo reduced homocysteine over 12 weeks in a 2023 randomized trial.

Timing tips: Take with meals; split morning/evening. Performance users often take part of the dose pre‑workout in studies.

Upper ranges: Studies span ~0.5–9 g/day in adults. Higher intakes raise the odds of GI upset and lipid changes—so stay conservative unless you have medical supervision.

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TMG vs folate vs vitamin B12 for homocysteine

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Practical tips for buying and using TMG

• Choose “betaine anhydrous.” That’s TMG for methylation—not betaine HCl (a digestive aid).
• Look for third‑party testing (NSF, USP, Informed Choice) and a short, clean ingredient list.
• Start low, go slow: Begin around 1,000–1,500 mg/day and titrate while watching tolerance and lipids.
• Cover the basics first: Regularly eat folate‑rich greens, get adequate B12, and hit your protein targets.

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Track what actually changes with BodySpec

Supplements are tools—but your results show up in your body composition and health markers.

• See your baseline clearly: A BodySpec DEXA scan quantifies total body fat, visceral fat, lean mass, and bone density with high precision. You’ll also see regional muscle balance (arms, legs, trunk) to spot asymmetries and guide training.
• Measure real progress: Re‑scan every 8–12 weeks to check whether your plan is reducing visceral fat and preserving or building lean mass. This is far more actionable than watching the scale alone.
• Keep prep consistent: Same time of day, similar hydration and meals, and avoid hard workouts right before your scan to keep readings comparable.

Ready to get objective data on your body composition? Book your BodySpec DEXA scan.

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FAQs

Is TMG the same as betaine?

Yes. “Betaine anhydrous” is TMG (the methyl‑donor form). “Betaine HCl” is a digestive acidifier and not used for methylation goals.

Can TMG replace creatine?

No. TMG may support your body’s creatine synthesis indirectly via methylation, but it’s not a substitute for creatine monohydrate. If creatine is your goal, see our creatine dosage guide.

What if my MTHFR status is uncertain?

You usually don’t need genetic testing. Most people start by ensuring adequate folate and B12. If homocysteine is elevated, discuss B‑vitamins with your clinician and consider TMG as an adjunct while monitoring lipids. Learn more in our guide to MTHFR.

Does taking TMG lower cardiovascular risk?

Not proven. TMG lowers homocysteine, but trials haven’t consistently shown improvements in vascular function or hard outcomes in generally healthy adults, as seen in a randomized FMD trial.

Do you offer RMR testing at BodySpec?

No. BodySpec focuses on DEXA body‑composition testing and currently does not provide RMR testing. You can still learn how RMR works in our educational overview: All About the RMR Test.

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This article is for educational purposes only and is not medical advice. Always consult your healthcare provider for personalized guidance.